The scene where Oscar Pistorius is alleged to have murdered his model girlfriend was reconstructed at his trial today.

The door through which 29-year-old Reeva Steenkamp was shot was brought into the court room, and then hit with a cricket bat as an expert witness demonstrated how the Paralympic athlete tried to beat it down in the aftermath of the fatal shooting.

A door frame was erected in the court this morning, and fitted with the door to the bathroom in Pistorius's Pretoria apartment. The door, with four bullet holes in it, was partially broken with splits in the wood.

A scale model of the toilet cubicle in the Blade Runner's home was also constructed, before police forensics expert Lieutenant Colonel Gerhard Vermeulen took to the witness stand.

Col Vermeulen, from the South African Police Services' forensic science lab, told the court he had examined the door to Pistorius' bathroom in March last year, several weeks after the Valentine's Day shooting.

He said marks on the door were consistent with it being hit or bashed with a cricket bat after the shots had been fired.

Col Vermeulen then took off his jacket, and demonstrated how the door could have been hit - first standing, and then while on his knees - at one point accidentally hitting the door itself, prompting giggles from the public gallery.

He went on to say the marks on the door indicated Pistorius did not have his legs on at the time.

But defence barrister Barry Roux challenged the expert witness on this conclusion, saying Pistorius would not have been able to balance while wielding a cricket bat if he had not been wearing his prosthetic legs.

Pistorius admits shooting 29-year-old Reeva in the early hours of February 14 last year, but denies murder. He claims he mistook his girlfriend for an intruder.